The purpose of this study is to estimate the averaged chemical structural model on the component of soil humic acid which was divided by the absorption chromatography using the hydrophobic resin DAX-8. Elemental and functional group analysis, ^1H-NMR, and ^<13>C-NMR, analysis were carried our on aromatic component and aliphatic component of the humic acid extracted from gray lowland soil (Entisol). In the ^<13>C-BNR analysis, CH, CH_2, and CH_3 subspectra were obtained by the DEPT method and the subspectrum of quaternary carbon was obtained by the QUAT method. The proportion of various form carbon was calculated in the every subspectrum. The proportion of the various form hydrogen was obtained from the -1H-NMR spectrum. The sum of aromatic carbon and phenol carbon of aromatic component is 55.6 % of all carbon, and it is very higher than that of the aliphatic component which is 21 % of total carbon. In the aromatic component, the number of end functional group (CH_3, CH_3O, and COOH) is
… More little 11 % of all carbon, and the total of aliphatic quaternary and tertiary carbon and O-C quaternary carbon is very little 3 %. Therefore, the aromatic component has the structure with small branding. The carbon of end functional group is abounding 29 % of total carbon on the aliphatic component, and the total of aliphatic quaternary and tertiary carbon is many 22 % of all carbon. The branching is abounding for the structure of the aliphatic component . The length of the aliphatic chain is very long, as sum total of CH_2 and CH_2O in the middle of aliphatic chain is many 28 % of all carbon. The molecular weight of structural unit was made to be 1500, molecular formula was obtained from the elemental composition, and it was assigned in various form carbon and hydrogen number that it calculated the functional group number from the functional group analysis and calculated the number of carbon and hydrogen of the remainder from NMR spectra. Chemical structure model which satisfied all data was proposed. Less